1. Field of the Invention
The present invention relates to an automatic exposure time control apparatus for a camera, particularly for reproducing the exposure time value stored as a digital value in the memory as the actual time.
2. Description of the Prior Art
Quite recently, many devices have been proposed in which the exposure time value is stored as a digital value and read out at the time of shutter opening in order to improve the exposure accuracy. In most of these devices, the shutter time values such as 1/1000 seconds, 1/500 seconds, 1/250 seconds, and so on, have values which are half of the next value which are stored as a digital value and are reproduced by making use of the count time of a binary counter. One of the most recently proposed devices is so designed that the shutter time values, one of which is one third (1/3) or one fourth (1/4) of the following value, are stored as a digital value and reproduced as the actual value in order to keep the reproducing error below 1/6 or 1/18. Such arrangement is disclosed in U.S. Pat. No. 3,995,284 (issued Nov. 30, 1976).
The exposure time reproducing method of the above automatic exposure time control apparatus is as follows. A digital signal (hereinafter called the decimal part of the exposure time value) of the exposure time value, which is smaller than one step of the value converted into digital value, is determined in such a manner that, for example, if the exposure time is controlled each by 1/3 step, one of the f (frequency), f (frequency).times.21/3 or f.times.22/3 is selected. The counting is carried out with the selected frequency as often as the number corresponding to the digital signal (hereinafter called the integral part of the exposure time value) representing the exposure time value for each one step so as to reproduce the exposure time. That is, in the case of the above automatic exposure time control apparatus, a reading out pulse signal with a certain specified frequency is provided in such a manner that the counting is carried out n times by making use of this reading out of pulses so as to reproduce the exposure time value. However, as mentioned above, it is necessary for the above automatic exposure time control apparatus to produce pulses with a certain specified frequency such as f.times.21/3 or f.times.22/3, which is very difficult to produce. Accordingly, in this conventional device, a complicated circuit composition is needed.